Metallurgical method for refining grains of steel by modifying inclusions through addition of magnesium and aluminum

Abstract

A metallurgical method for refining grains of steel includes adding aluminum into molten steel obtained from a secondary refining process. Aluminum reacts with oxygen and sulfur in the molten steel to reduce the total oxygen content in the molten steel to 15-120 ppm, to reduce a sulfur content in the molten steel to 15-150 ppm, and to produce aluminum oxide, obtaining cleaner molten steel. Magnesium is added into the cleaner molten steel and reacts with oxygen, sulfur, and aluminum oxide in the cleaner molten steel to reduce the total oxygen content in the molten steel to 10-60 ppm, to reduce the sulfur content in the molten steel to 5-100 ppm, and to produce inclusions including magnesium oxide, magnesium sulfide, and magnesium-aluminum spinel. Precipitates of the inclusions can serve as crystalline cores in a subsequent crystallization process to obtain fine-grained steel.

Description

technical field [0001] The invention relates to a steel smelting method, in particular to a smelting method for refining the steel grains by modifying inclusions in molten steel that have undergone secondary refining with magnesium and aluminum. Background technique [0002] Nowadays, molten steel smelted by Converter Steelmaking and Electric Arc Furnace (EAF) is often subjected to secondary refining through LF, VD, RH, VOD, VAD and other processes, so it is expected that the molten steel The content of phosphorus, sulfur, oxygen, nitrogen, and hydrogen is further reduced, and the content of carbon and alloys is adjusted reasonably, so that the content of components in the molten steel produced can be adjusted to an ideal range to meet the needs of modern steel products with various characteristics . [0003] The traditional steelmaking process is roughly divided into steps such as electric arc furnace steelmaking S91 or converter steelmaking S91' and secondary refining (Se...

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Problems solved by technology

[0006] The above-mentioned existing methods are not only costly but also have limited performance improvement. Taking the alloying technology as an example, it is necessary to rely on other high-cost alloying elements to enhance the strength and other properties of the steel, so that the strength of the steel is significantly improved. Due to the characteristics of the limited alloy elements, the operating cost is high, and the performance improvement of the steel usually does not exceed 20% (the yield strength does not exceed 600Mpa); in addition, taking the thermomechanical treatment process as an example, it can produce yield strength of 700~900Mpa However, in the process of controlled rolling and controlled cooling, various conditions of steel phase transformation, such as heating temperature, rolling speed or cooling speed, must be strictly controlled in order to accurately complete the refinement of steel grains , which requires a huge investment in equipment expansion, and the cost of energy consumption during operation is huge, so that the promotion of this thermomechanical treatment process is limited

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